Hi Alex, Thank you so much for swift and helpful response! The only Wav files written were: 19700101_010003.WAV (4.29 GB) 19700101_132541.WAV (1.93 GB) 19700101_132542.WAV (4.29 GB) I used the AudioMoth Filter Playground for the 1.93GB as you suggested and it says: AudioMoth 247475035FDF1F95 Recorded at 13:25:42 01/01/1970 (UTC+1) by AudioMoth 247475035FDF1F95 at low gain while battery was 4.1V and temperature was 25.2C. Recording stopped due to switch position change. I used a SanDisk Ultra 64GB with ExFat. If I set the recording period to 00:00 - 24:00 and use CUSTOM, I assume Audiomoth starts at midnight and not immediately? Would you recommend using a recording time (e.g. 1795s) or would it be OK to disable this function? I was just afraid that Audiomoth might have difficulties with handling a 10-12 GB WAV file Once again, thank you so much! Anton